pc wont boot even in safe mode after sp3 installation

hi guys,
just got my old pc running after 12 months being sat in the spare room, anyway to cut a long story short i installed sp3, after rebooting pc keeps going to black and white screen with safe mode etc on, when i try to boot in safe mode the pc gets stuck on the mups.sys file and wont go any further, if i try the last known good config option i get stuck in a loop bringing me back to the same page,i tried running it from restore cd, i then get an error saying there is no dump file ! please help
Carolyne